1. Technical Field
The present invention mainly relates to an ink-jet printer device and an ink-jet printing method.
2. Background Art
Conventionally, in an ink-jet printer using solvent ink, the solvent ink is discharged onto a medium, which is a print medium, from a print head (hereinafter, referred to as carriage), thereby forming an image. When an increase in printing speed is achieved, before ink discharged during first scanning is sufficiently fixed onto the medium, ink to be discharged during subsequent second scanning is discharged, whereby the ink discharged during the first scanning before fixation and the ink discharged during the second scanning are combined with each other on the medium in some cases. As a result, there arises a problem in that the ink moves on the medium, which leads to deterioration in image quality.
In order to solve the above-mentioned problem, in the conventional printer using solvent ink, as proposed in Japanese Patent Application Laid-open No. HEI 08-207262 and Japanese Patent Application Laid-open No. 2002-11860, for example, a heater for fixing ink is incorporated into a platen to carry out a control for fixing the solvent ink onto the medium in a shorter period of time. Temperature control for the platen is carried out such that a temperature detecting element is mounted to an inner surface of the platen so as to set an output temperature of the temperature detecting element to a constant temperature optimum for the medium.
However, in the prior art, the temperature control for the entire platen is carried out based on data from a single temperature detecting element mounted to the platen, that is, based on a temperature value measured in one section. As a result, the following temperature variations (temperature unevenness) occur.
First temperature unevenness occurs due to the fact that the temperature at ends of the platen becomes lower than that at a center thereof in a case where the platen is uniformly heated.
Second temperature unevenness is temperature unevenness caused in a sheet feed direction, that is, temperature unevenness in which the temperature of the medium on the platen at an upstream of the sheet feed direction becomes lower and the temperature thereof becomes a higher temperature close to a platen temperature toward the downstream thereof.
Third temperature unevenness occurs due to that fact that a difference between the platen temperature and the surface temperature of the medium is not constant because the heat conduction characteristic varies for each kind of the medium, whereby the necessary temperature of the medium surface varies.
Due to the above-mentioned temperature unevenness on the medium surface, there arises a difference in printed dot diameter. This is because, when the temperature of the medium surface is low, it takes time before the discharged ink dries, that is, before the discharged ink is fixed onto the medium, as compared with the portion of the medium surface in which the temperature is high, and an ink diameter is increased during that time. Accordingly, there is a problem in that the ink dot diameter varies for each temperature unevenness of the medium surface, which causes a sense of degradation in image quality.